This invention relates to a unique method for purification of sewage, waste water or potable water by thin film aeration and a special prefilter, described in Vandervelde and Helm's U.S. Pat. No. 4,997,568 Mar. 5, 1991. This is a division of Ser. No. 07/1711560 Filed May 30, 1991.
Historically, water purification has taken advantage, in some cases, of aerobic or anaerobic biological devices to produce improved effluent using biota fixed on a substrate, or suspended. Anaerobic devices have traditionally been limited to a maximum of about 70%-80% treatment and proposed as pretreatment stages prior to some further action, as in E. J. Jordon's (U.S. Pat. Nos. 3,950,252 April 1976 & 4,211,655 July 1980), A. A. Monson's (U.S. Pat. No. 4,162,976 July 1979), and A. W. Green's (U.S. Pat. No. 4,293,421 October 1981).
Sewage and waste water disposal is becoming a bottleneck in providing housing and employment for an increasing population. As sewage treatment standards become stricter and availability of clean water more restricted, the cost of providing these services rises. The result is people with substandard or unavailable housing and unemployment in many communities.
Extending and constructing standard municipal sewage plants to accommodate higher population densities is enviromnentslly unsound and becoming cost prohibitive. These systems inject poisonous disinfectants, pollute the surface water into which they discharge and prevent normal beneficial recharge of aquifers.
Standard on-site septic systems, to work well, require special soil and ground water conditions with large lot sizes. These factors are also becoming less available and more expensive as development proceeds. They discharge incompletely treated effluent into the environment.
More exotic and costly on-site septic systems designed to treat sewage under poor soil and ground water conditions are being used to fill the gap. These include Wisconsin Mound Systems, sand filters and a proliferation of types of mechanical aerobic reactors, many of which use the chemical disinfectants that repollute their effluent. These expensive systems do a passable job if designed, installed, and maintained properly. However, they seldom are because of their inherent complexity. This results in discharge of untreated or poorly treated sewage to pollute ground and surface water. Pumps and other mechanical devices that they require are often beyond the owner's financial capability, or interest, to maintain.
Commonly used sand and gravel falters rely on mechanical devices to increase the air/sewage interface by spraying, sparging, or spreading it over sand, gravel, or soil beds. This allows the growth of aerobic biota which treat the sewage. One of the most advanced and effective examples of this type is covered by U.S. Pat. No. 4,251,359, merchandised by SPEC Industries.
While investigating ultra-thin water film formation, we found that sewage caused to flow in a film over a hydrophilic surfaces, such as cotton cloth or sand, left its impurities behind and could then be released by gravity in liquid form into a collector. This resulted in a pooled, pure product free of odor and contamination while freeing the medium surface to absorb more film.
We believe that further review of patents and literature will not reveal a method or device which can accomplish this treatment as we have. Advantages of this invention are submitted in the Summary.